JPH0771604A - Cylinder head gasket - Google Patents

Abstract

PURPOSE:To make even the distortion amount of opening of a cylinder block even when the top deck portion of the cylinder block locally has a high-rigidity area. CONSTITUTION:A plurality of bores 17 as well as a head-bolt 13 insertion hole 18 are formed in a base plate 16 of a cylinder head basket 11. An annular shim 22 is secured to the periphery of each bore 17 located beneath the underside of the base plate 16. The shim 22 is used for adjusting the contact pressure surface pressure of the gasket with respect to a top deck 5 and a cylinder head 12. In a portion of the gasket 11 having the shim 22, the height of this portion contacting with the top deck portion 5 and the cylinder head 12 is set to be smaller at the area of the top deck 5 where the rigidity is high than at the area thereof where the rigidity is low. By this setting, the bearing- adjusting force of the shim 22 portion that corresponds to the high-rigidity-top- deck-portion 5 area becomes smaller than that of the shim 22 portion that corresponds to the low-rigidity-top-deck-portion 5 area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder head gasket interposed between a top deck portion of a cylinder block and a cylinder head in an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, a cylinder head gasket of this type has a bore hole for communicating the cylinder bore and the combustion chamber, and is interposed between the top deck portion of the cylinder block and the cylinder head when used. Then, these three members are fastened by head bolts.

The cylinder head gasket is required to have a function of sealing high temperature and high pressure combustion gas generated in the combustion chamber. Therefore, it is important to increase the contact pressure (contact pressure) generated between the periphery of the cylinder bore in the top deck portion and the periphery of the bore hole in the cylinder head gasket during fastening with the head bolt. Similarly, it is important to increase the contact pressure (contact pressure) generated between the periphery of the combustion chamber in the cylinder head and the periphery of the bore hole in the cylinder head gasket.

Therefore, a cylinder head gasket in which a hard and shim having a constant thickness is arranged around the bore hole has been put into practical use. It is also known that a grommet or a wire ring is used instead of the shim, or a bead is formed.

When the cylinder head is fastened to the cylinder block with the above cylinder head gasket interposed therebetween,
The cylinder bore may be distorted and the roundness may decrease.
This is because the top deck portion 53 of the cylinder block 52 is lifted to the cylinder head 54 side by tightening the head bolt 51, as shown by the solid line in FIG.
At this time, as compared with the circumference of the cylinder bore 56 in which the shim 55 is arranged, the head bolt hole 57 near the shim 55 is lifted more. As a result, the top deck section 53
The inclination is such that it becomes closer to the cylinder head 54 as it gets farther from the cylinder bore 56. Along with this, the bore wall 58 having the cylinder bore 56 is deformed outward (in the direction indicated by the arrow), and the circularity of the cylinder bore 56 is reduced. This problem also occurs when a grommet, a wiring, a bead or the like is used instead of the shim 55.

As a technique for dealing with the above-mentioned problem, for example, there is one disclosed in Japanese Utility Model Laid-Open No. 1-140070. In this technique, as shown in FIG. 9, a shim 61 is provided in the vicinity of the insertion hole 59 for the head bolt 51 and outside the bore hole 60 from the center of the insertion hole 59.
Such a configuration is devised as the distortion of the cylinder bore 56 is due only to the tightening force of the head bolt 51.

[0007]

However, the distortion of the cylinder bore 56 is related to not only the tightening force of the head bolt 51 but also the rigidity of the top deck portion 53.
For example, in recent years, in order to reduce the weight of an engine, it has been required to reduce its overall length (length in the cylinder arrangement direction). In order to meet this demand, it is considered that a bolt hole 63 into which a bolt 62 for mounting an engine mount is screwed is provided in the cylinder block 52 as shown by a chain double-dashed line in FIG.

In this case, the boss portion 6 having the bolt holes 63
When the top deck portion 53 and the bore wall 58 are connected by the boss 4, the boss portion 6 is attached to the top deck portion 53.
The rigidity of the portion corresponding to 4 becomes higher than that of other portions.
Then, the tightening force of the head bolt 51 with respect to the top deck portion 53 is also transmitted to the bore wall 58 via the boss portion 64, and the bore wall 58 is pulled. Therefore, the bore wall 58 is further deformed by the amount of this pulling, and the cylinder bore 5
6 is greatly distorted.

Therefore, in the technique of the above publication in which the rigidity of the top deck portion 53 is not taken into consideration, the deformation of the bore wall 58 due to the boss portion 64 cannot be dealt with completely, and the cylinder bore 5 is prevented.
There is a problem that the distortion of 6 cannot be reduced sufficiently.

The present invention has been made in view of the above-described circumstances, and an object thereof is to open a cylinder block corresponding to a portion having a high rigidity even if there is a portion having a high rigidity in the top deck portion of the cylinder block. (EN) A cylinder head gasket capable of suppressing a part of the peripheral portion of a hole from being deformed more than other parts, and making the strain amount of the opening uniform.

[0011]

In order to achieve the above object, the present invention is interposed between a top deck portion of a cylinder block and a cylinder head which are fastened to each other by a fastening member, and the fastening member tightens the top. The deck part and the cylinder head are pressed against each other to seal the two, and contact pressure is applied to the top deck part and the cylinder head around the holes provided in the cylinder block or the cylinder head. A cylinder head gasket having an annular surface pressure adjusting means for adjusting, wherein the surface pressure adjusting force of a portion of the surface pressure adjusting means corresponding to a high-rigidity top deck portion is adjusted by the rigidity of the surface pressure adjusting means. It is set to be smaller than the surface pressure adjustment force of the part corresponding to the low top deck part.

[0012]

[Function] A cylinder head gasket is interposed between the top deck of the cylinder block and the cylinder head,
When these are fastened to each other by the fastening member, the top deck portion is lifted to the cylinder head side. At this time, the top deck portion is lifted higher in the vicinity of the fastening member where the surface pressure adjusting means is disposed than in the vicinity of the opening of the cylinder block or the opening of the cylinder head. As a result, the top deck portion inclines so as to approach the cylinder head as the distance from the opening increases. Along with this, the peripheral portion of the opening in the cylinder block is deformed outward. The amount of deformation at this time varies depending on the rigidity of the top deck portion. That is, at a location with high rigidity, the fastening force of the fastening member reaches the peripheral portion of the opening, and the portion is strongly pulled toward the fastening member.

On the other hand, in the present invention, the surface pressure adjusting force of the portion of the surface pressure adjusting means corresponding to the high-rigidity top deck portion of the portion corresponds to the surface pressure adjusting means of the low-rigidity top deck portion of the surface pressure adjusting means. It is set smaller than the surface pressure adjustment force. For this reason, in the top deck portion, the lifting amount in the vicinity of the fastening member in the high rigidity portion is smaller than the lifting amount in the vicinity of the fastening member in the low rigidity portion. Then, the peripheral portion of the opening is strongly pulled at the high rigidity portion by the tightening force of the fastening member, but the deformation amount of the peripheral portion of the opening due to the pulling is offset by the decrease in the lifting amount in the top deck portion. As a result, regardless of the rigidity of the top deck portion, the distortion amount of the opening becomes almost uniform at any part.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment in which the present invention is embodied in a cylinder head gasket applied to a multi-cylinder engine is shown in FIG.
~ It demonstrates according to FIG.

As shown in FIG. 2, a cylinder block 1 of an engine is formed with a plurality of substantially cylindrical bore walls 2 having open upper and lower ends. Inside each bore wall 2 is a cylinder bore 3 as an opening of the cylinder block 1, in which a piston is reciprocally housed. A water jacket 4 is formed around the bore wall 2. The water jacket 4 is a passage through which cooling water for cooling the bore wall 2 and the combustion chamber passes. A plurality of head bolt holes 6 are formed around each bore wall 2 in a top deck portion 5 which constitutes an upper portion of the cylinder block 1.

In order to shorten the overall length of the engine (the length of the bore wall 2 in the arrangement direction), a plurality of bolt holes 7 are formed in one side portion (left side portion in FIG. 2) of the cylinder block 1. . These bolt holes 7 are for mounting bolts 8 when mounting the engine mount on the cylinder block 1.
Is a hole into which is screwed. More specifically, as shown in FIGS. 1 and 2, a boss portion 9 having a bolt hole 7 extending in the arrangement direction of the bore walls 2 is provided in the cylinder block 1. The boss portion 9 connects the top deck portion 5 and the bore wall 2 to each other. Therefore, the top deck section 5
In, the rigidity of the portion corresponding to the boss portion 9 (the portion surrounded by the alternate long and short dash line in FIG. 2) is higher than the other portions where the boss portion 9 is not provided.

As shown in FIG. 1, the top deck portion 5
A cylinder head 12 is laid over the cylinder head gasket 11 with a cylinder head gasket (hereinafter, simply referred to as a gasket) 11 interposed therebetween. These three members 5, 11 and 12 are fastened and fixed by a plurality of head bolts 13 as fastening members. A combustion chamber 15 is formed in the cylinder head 12 at a position corresponding to the cylinder bore 3.

The gasket 11 has a substrate 16 having elasticity. The substrate 16 is formed of a metal plate having a constant thickness at any part. A bore hole 17 is formed in the substrate 16 at a location corresponding to the cylinder bore 3 and the combustion chamber 15 so that the bores 3 and 15 communicate with each other. Further, the head bolt 13 is provided on the substrate 16.
A through-hole 18 for use is formed. An annular bead 21 is formed around each bore hole 17 of the substrate 16.
Each bead 21 protrudes to the lower side (top deck portion 5 side),
And it has an arcuate cross section. These beads 21 are used for the cylinder head 1 when the head bolt 13 is tightened.
The lower surface of 2 and the upper surface of the top deck portion 5 are elastically pressed against each other.

On the lower surface of the substrate 16, an annular shim 22 having a predetermined thickness is fixed between the peripheral edge of each bore hole 17 and the bead 21. The shim 22 constitutes a surface pressure adjusting means for adjusting the contact pressure (surface pressure) of the gasket 11 against the top deck portion 5 and the cylinder head 12. More specifically, the gasket 11 is required to have a function of sealing high temperature and high pressure combustion gas generated in the combustion chamber 15 during engine operation. Therefore, the shim 22 increases the surface pressure generated between the periphery of the cylinder bore 3 in the top deck portion 5 and the periphery of the bore hole 17 of the gasket 11. Similarly, the periphery of the combustion chamber 15 in the cylinder head 12 and the gasket 1
The shim 22 increases the surface pressure generated between the bore hole 17 and the periphery thereof.

In this embodiment, as shown in FIGS.
The thickness of the shim 22 in the top deck portion 5 where the rigidity is high (the location surrounded by the alternate long and short dash line in FIG. 3), that is, the location where the boss portion 9 is provided is smaller than the thickness of other locations where the rigidity is low. Is also set small. In other words, in the portion of the gasket 11 having the shim 22, the intervals between the portions in contact with the top deck portion 5 and the cylinder head 12 are t1 and t2. The interval t1 is an interval at a highly rigid portion of the top deck portion 5 (on the left side in FIG. 4). The interval t2 is an interval at a low rigidity portion of the top deck portion 5 (on the right side in FIG. 4). In this embodiment, t1 <
The intervals t1 and t2 are set so as to be t2. With this setting, the high-rigidity top deck portion 5 of the shim 22
The surface pressure adjusting force of the portion corresponding to (1) is smaller than the surface pressure adjusting force of the portion of the shim 22 corresponding to the low-rigidity top deck portion 5.

As a method of changing the thickness of the shim 22 only partially, as described above, a method of pressing only a predetermined portion of an annular shim material having a constant thickness to reduce the thickness, and a thick C shape are used. Any method may be used in which a thin shim material, which is a separate member, is bonded to the remaining portion of the shim material.

Next, the operation and effect of this embodiment configured as described above will be described. As shown in FIG. 1, a gasket 11 is interposed between the top deck portion 5 and the cylinder head 12, and these are fitted with a plurality of head bolts 13.
The top deck portion 5 is lifted to the cylinder head 12 side in a state where they are mutually tightened by. At this time, the top deck portion 5 has the cylinder bore 3 in which the shim 22 is arranged.
The head bolt hole 6 without the shim 22 is lifted higher than the surrounding area. As a result, the top deck 5
Is farther from the cylinder bore 3
Incline toward. Along with this, the bore wall 2 is deformed outward (in the direction indicated by the arrow).

The amount of deformation at this time depends on the rigidity of the top deck portion 5. That is, at the location where the boss portion 9 is provided, the top deck portion 5 and the bore wall 2 are connected by the boss portion 9, and the rigidity of the top deck portion 5 is increased. Therefore, when the top deck portion 5 is lifted, the tightening force of the head bolt 13 at that time is transmitted to the bore wall 2 via the boss portion 9, and the bore wall 2 is further pulled outward. Therefore, assuming that the thickness of the shim 22 is uniform in all parts, the high-rigidity part having the boss portion 9 is further deformed as shown by the chain double-dashed line in FIG.

However, in this embodiment, the shim thickness is set in consideration of the rigidity of the top deck portion 5,
Interval t2 at a high rigidity location than interval t2 at a low rigidity location
1 is smaller. That is, the surface pressure adjusting force of the portion of the shim 22 corresponding to the high-rigidity top deck portion 5 is made smaller than the surface pressure adjusting force of the portion of the shim 22 corresponding to the low-rigidity top deck portion 5. For this reason, the head bolt 1 at the high-rigidity area is more
Lifting amount near 3 is reduced. Then, the boss 9
Even though the bore wall 2 is strongly pulled by
The amount of deformation of the bore wall 2 due to the pulling is offset by the decrease in the amount of lifting. As a result, the amount of strain of the bore wall 2 can be made substantially uniform regardless of the rigidity.

Further, according to this embodiment, the gasket 1
The gas sealability of 1 is improved. This is because at the high rigidity portion of the top deck portion 5, the tightening force of the head bolt 13 directly acts on the peripheral edge portion of the cylinder bore of the top deck portion 5 via the boss portion 9, so that the shim 22 and the top deck portion 5 are connected.
The surface pressure between them becomes higher than the surface pressure in the parts other than the high rigidity. At this time, if the thickness of the shim 22 is constant, the surface pressure between the shim 22 and the top deck portion 5 at a position slightly apart from the boss portion 9 becomes high at the high rigidity portion. It decreases by the amount. Therefore, the combustion gas may leak from the location where the surface pressure is reduced.

On the other hand, in this embodiment, since the thickness of the shim 22 corresponding to the high-rigidity portion of the top deck portion 5 is reduced, the surface pressure of the same portion correspondingly becomes low.
Due to this decrease in surface pressure, the surface pressure becomes almost constant at any part of the shim 22. Therefore, the gas sealability can be improved and gas leakage can be eliminated.

The present invention is not limited to the configuration of the above-mentioned embodiment, and may be arbitrarily modified within the scope not departing from the spirit of the invention as follows. (1) As the surface pressure adjusting means, the shim 22 in the above embodiment is used.
Instead, a wire ring 23 and a grommet 24 as shown in FIG. 5 may be used. The wire ring 23 is fitted on the inner peripheral edge of the bore hole 17 of the graphite substrate 16 and is locked by a grommet 24 formed into a U-shaped cross section. In this case, the distance between the upper surface and the lower surface of the grommet 24 corresponds to the distances t1 and t2 in the above embodiment. The left side portion of FIG. 5 corresponds to a highly rigid portion of the top deck portion 5, and the wiring 23 is crushed in advance.
The right side portion of FIG. 5 corresponds to a portion of the top deck portion 5 having low rigidity. The intervals t1 and t2 are set so that t1 <t2 holds.

(2) As the surface pressure adjusting means, a bead 25 as shown in FIG. 7 may be used instead of the shim 22. FIG. 3A shows an example in which one bead 25 is formed on the substrate 16. Further, (b) shows an example in which other substrates 26 and 27 are laminated on both sides of the substrate 16 and the beads 25 are formed on them. In the case of (a), the height of the bead 25 (the distance between the upper surface of the substrate 16 and the lower end surface of the bead 25) corresponds to the distances t1 and t2 in the above embodiment. In the case of (b), the distance between the upper end surface of the upper bead 25 and the lower end surface of the lower bead 25 corresponds to the distances t1 and t2 in the above embodiment.

(3) In FIG. 7 (a), the surface pressure adjusting force is changed by adjusting the height (interval t1, t2) of the bead 25, but as shown in FIG.
May have the same height (interval t1), and the bead widths w1 and w2 may be adjusted to change the surface pressure adjusting force. The left side portion of FIG. 6 corresponds to a high rigidity portion of the top deck portion 5, and the right side portion corresponds to a low rigidity portion of the top deck portion 5. Each bead width is w1 so that the surface pressure adjusting force of the portion of the bead 25 corresponding to the high-rigidity top deck portion 5 becomes smaller than the surface pressure adjusting force of the portion corresponding to the low-rigidity top deck portion 5. > W2 is set.

(4) The embodiment and the other examples (1) to
In (3), the surface pressure adjusting means around the bore hole 17 has been described, but this surface pressure adjusting means may be applied around other water holes, oil holes and the like.

[0031]

As described above in detail, according to the present invention, the surface pressure adjusting force of the portion corresponding to the high-rigidity top deck portion of the surface pressure adjusting means is adjusted to the top deck having low rigidity of the surface pressure adjusting means. Since it is set to be smaller than the surface pressure adjustment force of the part corresponding to the part, even if there is a part with high rigidity in the top deck part, part of the surrounding part of the opening of the cylinder block corresponding to that part This has an excellent effect of suppressing the deformation to a greater extent than other portions and making the strain amount of the opening uniform.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a state in which a cylinder head is fastened to a cylinder block with a cylinder head gasket interposed therebetween in an embodiment embodying the present invention.

FIG. 2 is a partial plan view of a cylinder block according to an embodiment.

FIG. 3 is a plan view of a cylinder head gasket of one embodiment.

4 is a partially enlarged cross-sectional view taken along the line AA in FIG.

FIG. 5 is a partial cross-sectional view of a cylinder head gasket showing another example in which wiring and grommets are used instead of shims.

FIG. 6 is a partial cross-sectional view of a cylinder head gasket showing another example in which beads are formed instead of shims.

7A and 7B are partial cross-sectional views of a cylinder head gasket showing another example in which beads are formed instead of shims.

FIG. 8 is a partial cross-sectional view showing a state in which a cylinder head is fastened to a cylinder block with a conventional cylinder head gasket interposed therebetween.

FIG. 9 is a bottom view of a conventional cylinder head gasket.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cylinder block, 3 ... Cylinder bore as an opening of a cylinder block, 5 ... Top deck part, 11 ... Cylinder head gasket, 12 ... Cylinder head, 13 ...
Head bolts as fastening members, 17 ... bore holes, 22 ...
Shims as surface pressure adjusting means, 23 ... Wiring as surface pressure adjusting means, 24 ... Grommets as surface pressure adjusting means, 25 ... Beads as surface pressure adjusting means

Claims (1)

[Claims] 1. A cylinder block is interposed between a top deck portion and a cylinder head, which are fastened to each other by a fastening member, and the fastening member fastens the top deck portion and the cylinder head to seal them. At the same time, a cylinder head gasket having an annular surface pressure adjusting means for adjusting the contact pressure to the top deck portion and the cylinder head is provided around the hole provided in the opening of the cylinder block or the opening of the cylinder head. The surface pressure adjusting force of the portion of the surface pressure adjusting means corresponding to the high-rigidity top deck portion is smaller than the surface pressure adjusting force of the portion of the surface pressure adjusting means corresponding to the low-rigidity top deck portion. Cylinder head gasket characterized by being set.